Using Cisco Unified Communications Manager to Configure MGCP Gateway Support
Configuring MGCP Gateway Support
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Cisco VGD 1T3 Voice Gateway Software Configuration Guide
Switchback
Switchback is the process a voice gateway uses to reestablish communication with the primary
Cisco Unified Communications Manager server when the server becomes available again. Switchback
can occur immediately, at a specified time after the last active call ends, or after a specified length of
time.
MGCP Gateway Fallback
The MGCP gateway maintains a remote connection to a centralized Cisco Unified Communications
Manager cluster by sending MGCP keepalive messages to the Cisco Unified Communications Manager
server at 15-second intervals. If the active Cisco Unified Communications Manager server fails to
acknowledge receipt of the keepalive message within 30 seconds, the gateway attempts to switch over
to the next available Cisco Unified Communications Manager server.
If none of the Cisco Unified Communications Manager servers respond, the gateway switches into
fallback mode and reverts to the default H.323 session application for basic call control. H.323 is a
standardized communication protocol that enables dissimilar devices to communicate with each other
through use of a common set of codecs, call setup and negotiating procedures, and basic data transport
methods. The gateway processes calls on its own using H.323 until one of the Cisco Unified
Communications Manager connections is restored.
Figure 2
illustrates a typical VoIP network topology in which MGCP gateway fallback is supported.
Figure 2
Typical VoIP Network Topology Supporting the MGCP Gateway Fallback Feature
The MGCP Gateway Fallback feature provides the following functionality:
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IP
IP
WAN
LAN
Cisco
router
Cisco
router
LAN
MGCP/H323
MGCP/H323
POTS
POTS
IP phones
IP phones
PBX phone
FXS
T1/E1 PRI
FXO
PBX
T1-CAS
PSTN
Remote site A
Remote site B
LAN
M
M
M
Cisco Unified
Communications Manager
1
Cisco Unified
Communications Manager
2
Cisco Unified
Communications Manager
3
Cisco Unified
Communications Manager
cluster